Currently used electroluminescent materials and electroluminescent elements using the same can be roughly classified into two groups, i.e., inorganic materials and organic materials. Inorganic electroluminescent materials are superior to organic electroluminescent materials in long-term stability, and emit light even under high temperatures or other severe conditions. Therefore, further research and development of inorganic electroluminescent materials are sough.
As disclosed in Trigger, vol. 18, No. 3 (1999): pp. 21-23, among inorganic electroluminescent materials, only a material using an electroluminescent layer formed from ZnS to which Mn is doped as an impurity (dopant) has been put into practical use. However, such an electroluminescent material emits only light with a specific wavelength, in particular yellow light, and therefore emission of non-yellow light using electroluminescence has not yet been achieved.
Emission wavelength in electroluminescence is determined by the electronic state specific to the electroluminescent material used. Therefore, in order to emit light other than yellow light, development of electroluminescent materials other than Mn-doped ZnS is required. Currently, research and development of electroluminescent materials that emit red light having a wavelength longer than yellow light, and blue, green or other light having a wavelength shorter than yellow light have not been progressed satisfactorily. With this being the situation, the development of electroluminescent materials that emit high-luminance light with little energy consumption, have little energy loss due to conversion to heat, etc., suffer from little deterioration even after long-time usage, and, in particular, inorganic electroluminescent materials that emit blue, green or other light having a wavelength shorter than that of yellow light have been awaited.